Automatic system for supplying pulverized fuel to furnaces



AUTOMATIC YsTEM FOR SUPPLYING PULVERIZED FUEL TO FURNACES E. V. FRANCIS Dec. 2 193?.

Filed Jan. 18, 1955 4 Sheets- Sheet 1 N VE/YTOR Ear/e V F7anci zaf ATT'Y E. v. FRANCIS 2,3G2fi91 AUTOMATIC SYSTEM FOR SUPPLYING PULVERIZED FUEL TO FURNACES Fi led Jan. 18, 1955 4 Sheets-Sheet 2 //VVE/Y TOR far/e V fianc/s ATT'Y.

Patented Dec. 21, 1937 2,102,091 an'romgrc SYSTEM roa'snrrume PUL- RIZED FUEL T FURNACES Earle V. Francis, Columbus, Ohio, assignor to The Jeffrey Manufacturing Company, a cor poration of Qhio Application January 18, 1933, Serial No. 652,347

1. Clailm.

My invention relates to automatic systems for controlling the supply of pulverized coal to furnaces and one of the objects of the invention is the provision of improved and efficient thermostatically controlled apparatus for starting and stopping the operation of a furnace and feed- Other objects of theinvention will appear hereinafter, the novel features and combinations being set forth in the appended claim.

Referring to the accompanying drawings, Fig. 1 is an elevational view with the furnace shown in sect-ion, of my improved automatic system for burning pulverized coal;-

Fig. 2 is a front elevation of the installation shown in Fig. 1;

Fig. 8 is a sectional elevation of the stack switch mechanism, taken on the line 3-3 of Fig. 4 looking in the direction of the arrows;

Fig. 4 is an elevational view of the stack switch mechanism with the front cover removed;

Fig. 5 is a sectional elevation of the feeding and mixing mechanism shown at the lower right hand portion of Fig. 1, the section being taken along the line 5-5 of Fig. 8 looking in the direction of the arrows; 1

Fig. 6 is an elevational view partly in section of that portion of Fig. 5 to the left of the fan shaft therein; 1

Fig. 7 is an enlarged sectional elevation of the burner nozzle for the furnace-with the electric ignitor attached thereto; v

Fig. 8 is a plan view of the feeding and mixing mechanism shown in Figs; 5 and Gbut with the storage bin removed;

Figs. 9 and 10 are broken away portions of Fig; 4 showing positions of the parts during the starting and running periods respectively;-

Fig. 11 showsa wiring diagram of the circuits and connections for the automatic system;

Fig. 12 is a modified wiring diagram embodying an additional safety feature; and

Fig. 131s another modified'wiring diagram embodving another safety feature. In Fig. 1, l4 designates a furnace of the vertical type and may be either in a hot air heating vapor heating system or steam heating system,

while my improvements are particularsystem. 1y adapted to furnace already in operation for theburning of f the delivery of fuel to a furnace and rendering safe the operation ofthe furnace..

' plate 51.

be installed in connection with a coal in the ordinary manner, it should be understood that my system may be permanently or detachably connected to a furnace when initially installed. Upon removal of the ordinary fire door ofa previously installed furnace an ignition or preliminary combustion chamber l5 may be placed in the furnace chamber l8 by inserting through the fire door of the furnace a casing H which. is lined with refractory or fire resisting material l8 and which is provided with an opening at l8 in its bottom to communicate with the furnace cham-- her It. The casing i1 is secured to a plate 20 which in turn is secured to the front of the furnace to close the fire door opening therein.

Secured to the front face of the plate by means of the radial flange or plate 2| is a-burner nozzle 22 which has its inner end 23 projecting into the auxiliary or preliminary combustion chamber-l5. The nozzle 22 is preferably conical as shown in Fig. 7 with its rear end screw threaded at 24 forconnection to the pipe 25 which leads to the pipe 26 and casing 48 in which is mounted a blower or fan 21 as shown in Fig. 5.

The powdered fuel such as pulverized coal is adapted to be stored in the large bin or casing 28 the lower end of which is conical orhopper' shap'ed as shown-at 29 in Fig. 1. The upper end of the casing 28 is provided with a filling opening at 88 through which the pulverized coal may be placed in the bin 28 after removal of the cover 3|. In order to prevent coal dust from flying about in the furnace room and to protect the persons performing the filling operations a vacuum cleaner may be connected through the suction pipe I84 to the interior of the bin 28 as shown in Fig. '1.

To the lower end of the hopper-shaped portion 29" of the pulverized coal bin 28 is secured a casting 32 which is provided with an annular groove 83 to receive a felt packing 34 shown in Fig. 5, the latter serving to prevent leakage of pulverized coal from the annular portion 59 of The pulverized coal bin and to the lower end of these standards is secured a base frame 38 on which is mounted the worm gear housing 31 as shown in Fig. 5. Mounted in the bearings 41, 48 is a shaft 48 which is connected at one end 4| to the fan wheel 21. The other end of the shaft '48 is coupled at 42 to the shaft 43 and the latter is connected to 28 may be mounted on I spaced vertical standards 35 as shown in Fig. 1 45 the armature of the electricmotor 44. Upon rotation of the .motor 44 in the proper direction the fan 21 will operate to take a mixture of powdered coal and air through the intake opening 450i the fan housing 48 and blowv such through the pipe 28 into the pipe 25 and thence into and through the nozzle 22 into the preliminary combustion chamber l5. Thrust bearings for the shaft 40 are provided at 41, 48 as shown in Fig. 5 and associated with such thrust bearings are suitable lubricating openings.

Secured rigidly to the top of the worm gear housing 31 instationary position is a circular support or ring 49 which is provided with an inner annular groove 50 to receive a felt packing 5|. The inner lower portion'of the ring 49 carries a spider frame 52 comprising a plurality of arms inclined upwardly and secured at their upper ends to the thrust bearing support 53.

A vertical shaft 54 coaxial with the ring 49 is provided with stepped thrust roller bearings at its lower and intermediate portions. The lower thrust bearing 55 resists movement of theshaft 54 upwardly and the upper thrust bearing 56 resists downward movement of the shaft 54 relative to the bearing support 53 and the parts secured thereto.

Secured to the enlarged upper end of the shaft 54 is a feed plate 51 the upper surface of which is provided with a spiral groove 58 as shown in Figs. 5 and 8. The inner end of the spiral groove is the leading end relative to the direction of rotation of the feed plate 51 and the end of the groove at the periphery of the feed plate 51 is the trailing end so that when the feed plate rotates in an anti-clockwise direction as viewed in Fig. 8 the spiral groove 58 will produce friction between the plate 51 and the powdered coal in the hopper 29 tending to prevent the plate from sliding under a stationary mass of powdered coal. Furthermora' due to the spiral groove. any such sliding will assist in conveying the central portions of the powdered coal on the feed plate 51 to the periphery thereof.

The feed plate 51 has connected to the lower peripheral edge thereof an annular portion 59 the upper peripheral surface of which engages the bottom of the felt packing 94 so as to effectually confine the powdered fuel in the annular passageway 66 which is below the horizontal plane of the upper surface of the annular portion 59 of said feed plate 51. p p

Also secured to the feed plate 51 is a depending annular flange 6| the outer surface of which engages the felt packing 5| so that lubricating oil thrown onto the thrust bearings 55, 56 and the annular gear 62 by rotation of the collars I 63, I63, will not leak out from the ring 49.

On the interior of the depending annular flange 6| is an annular gear 52 with whlch'meshes a pinion 63 at the upper end of the vertical shaft 64 as shown in Fig. 6. The'shai't 84 is mounted to rotate in the bearings 65, 65 and between these bearings the shaft 64 is keyed to a worm gear 61 with which meshes a worm 68 on the shaft 40. It will thus be seen that when the motor 44 shown in Fig 1 is rotated, power will be transmitted through the worm gearing 68, 61 and the spur gearing 63, 62 to efl'ect rotation of the feed plate 51. Such rotation should be in an anticlockwise direction as viewed in Fig. 8 so that the inner end of the spiral groove 58 will lead and the outer end will trail so as to effectually transfer the powdered fuel without caklng to the annular passage-way 66.

The upper central portion of the feed plate 51 is provided with a hub 69 to which is secured at 10, 10' an agitator 1| which has an arm inclined upwardly for travel along a conical path parallel to the inner surface of the conical hopper 29 and adjacent thereto. The agitator 1| co-operates with the grooved feed plate to secure transfer of the powdered fuel from all portions of the bot- 2,1oaca1 tom of the hopper 29 to the annular passageway 60. l

By referring to Figs. 5 and 8 it will be seen that the inner surface of the casting 32 is conical at 12 in conformance with the inner surface of the hopper 29 except that an opening is provided at 13 for the passage of the pulverized fuel into the annular passage-way 60. The inner lower edge of the surface 12 overlaps the peripheral edge of the feed plate 51 and is located closely adjacent thereto. Also closely adjacent to the upper surface of the feed plate 51 is a pointed triangular deflector 14 secured at 15, 15 to the casting 92 so as 'to occupy a stationary position and so as to be adapted to deflect pulverized coal from the plate 51 over an area extending I have provided radial spaced apart loops of wire attached to feed plate 51, as shown at 16, 16 in Figs. 5 and 8. I prefer to locate these wire loops so as to travel closely adjacent to the top of the passage-way 60 formed by the flat annular surface below the conical surface 12 of the casting 32 so'that the material will not tend to adhere to such flat annular surface.

As a further assurance that the pulverize coal will not form in lumps or become caked I have provided radial grooves 11, 11 in the upper surface of the feed plate 51.

On that side of the hopper bottom casting 32 diametrically opposite the opening 13 is an adjustable plow 19 mounted in position for the annular flange 59 to slide under the same as shown in Figs. 5 and 8. The plow 19 is secured to a vertical rock shaft mounted in bearings in a bracket 8! on the casting 32. 'A collar 82 secured to the vertical shaft 9 0 is provided with an outwardly projecting or radial pin 83 which is adapted to fit into a slot 84 atthe lower end of the arm 85 of a bell-crank lever 86 which is pivoted at 81 to the'upper end of the bracket 89.

The horizontal arm 88 of the bell-crank lever 86 extends through a loop 89 secured to the upper end of the vertical rod 99. A spring surrounds the rod 9!) between the plate 92 which is secured to the upper end of the rod 99, and the shelf 93 which extends laterally from the casting 32. The spring 9i presses upwardly against the plate 92 tending to hold the rod 99 in its uppermost position. The upper limit of the rod 99 may be adjusted by the nuts 94 which are screw threaded on rod 95 secured to the lower end 9 the rod 90.

On'the base frame 35 is mounted by means of 7 the bolts 9|; the solenoid 91. A plunger 98 ex tends downwardly into the solenoid 91 and at 99 to the upper end of the plunger 98 is pivoted a screw threaded rod I09. A connector wt provided with right handed screw threads is mounted on the screw threaded rods 95,106. By removing the pivot pin at 99 and turning the screw I00 and reconnecting the pivot pin the position of the plunger 98 may be adjusted relawill cause the loop 89' to swim downwardly the arm 88 and consequently the shaft 80 will be rotated to swing the plow 19 in a clockwise dicenter of the feed plate 51 to a running position. It can readily be seen that by means of the;

nuts 04 the running'position of the. plow 19 may be adjusted so as to scoop pre-determined quantitles of powdered coal from the trough 60 during each rotation of the feed plate 51.

On top of the nozzle 22 as shown in Fig. 7 is mounted an electric spark gap'igniter I03 comprising a lower terminal connected to the metal of the nozzle 22 and an upper terminal mounted in insulating materialIM. The terminals of the spark gap igniter I03 are electrically connected to a transformer I05 (Fig. 11 in the'ignition box I06 (Fig. -2). v H

An illuminating gas supply pipe I 01; is connected as shown in Fig. '7 to the gas burner nozzle I08 which is preferably in alignment with the air intake port I00. An electromagnet 0 as shown in Fig. 11 is adapted to open and close a valve III in the gas pipe I01. A manually operated regulating valve I I2 mayalso be located in the gas supply pipe I01. At the same time that the spark gap igniter I03 is operated the electro-magnet IIO acts to open the valve III and. therefore during the flow of gas through the nozzle I08the igniter is operating and air is drawn into the intakeport I09. p v

Extending into the outletfiue II3 of the furnace I4 is anelectric stack switch'device II4 which is shown in Fig. 4 with its cover removed. This stack switch device comprises a thermostatic element I I5 which is in position to receive the heat from the flue gases and thereby rock the shaft IIB to the outer end of which are freely pivoted two mercury switch carrying plates II1, Clutch means including springs II 9, I are relied on to effect rotating of the carriers H1, III) with the shaft II6 until the carriers are stopped by means of abutments, The rear carrier II 3 is limited in its arcuate movement by striking against the abutments I2I, I22 shown in Fig. 4, while the front carrier I I1 has a larger arcuate movement and islimited by the adjustable abutments I23, I24."

The rear carrier I I8 carriesthe hold-in mercury switch. I26 while the front carrier, II 1 carries the pull-in mercury switch I and the ignition mercury switch I2 1.'

Below the outer end, oirthe rock shaft H6 is mounted an electro-magnet, l.32 having a winding I28 and. adjacent the pole I29 of this elec tro-ma'gnet is a pivoted armature I30'.' This armature has mounted thereon a mo'tor mercury switch I3I controlling the motor, circuit so that 'wh'en-thearmature 130 is attracted tolthe pole I 29 thec ircuit of the electric motor 44. [will be closed].v Q Pivotally mounted at I32, on the frame fof thej electro-magnetI32 is a lookout mercury switch "I33 held normally I in closed position by the trippingdevice I34. Wound on insulating ma terial is a resistor or electric heater I35 under an expansion element I 36 as' shown inFig. 4. .When

this resistor receives a certain amount of current for a 'sufficient .leng'th of time the.tripping device I34 will beoperated to release the switch I 33 and the latter will be tilted in a' clockwise direction as viewed in Fig. 4 to open the supply circuit. The supply circuit cannot. again be energized'until thetripping device has been reset,

manuallyv at I 31. I

The 'electro-magnet I32 also comprises two transformers comprising. one primary winding I38 and two secondary windings I28 and I39. j

The operation of the system will be understood by referring to Fig's. 3,4,and 11. When thejfurnace is not operating the stack switch" device II4 will have its parts located as shown in Fig. 4

switch I3I open, the pull-in switch ]l2'5. .closed, the hold-in switch I26 open, and the ignition switch I21 closed. 'When'the room thermostat mercury switch I40 moves to closed position as shownin Fig. 11 current flows through thepri mary I38 of the transformer of the electro-mage net I32 provided the mainline switch MI is closed. The circuit will befrom themain I42,

through the switch I4I, conductor I43, switch I33, primary I38, conductors I44, I to the other supply main I 46. The closureofthis' c1r-' cuit will furnish suflicient voltage to the secondary I28 to cause sufiicient" current toflow through thefcon ductor l41', switch I25, conductor I48, resistor I 35, conductor I 49-, thermostat switch I 40,?and conductor I50, toenergiZ'e' theele'ctro magnet I3 2jto cause its armature I30 to tilt the mercury switch I3I to 'f'closed position as shown in Fig. 11. It should be particularly noted. that in order to enable the electro-magnet to attract the armature I30 and close the switch 'I3I the pull-inswitch' I25 must be closed. I

Immediately upon'the' closure of the switch I3I current will be suppliedto the motor 44 through livery to the fan21 which rotates immediately upon the starting of the motor 44. Also simultaneously with the starting ofjthe motor 44 the electro-magnet I I0is, energized to; efiect the opening of the valve .III to eifect a flow of gas through the pipe I01 into the nozzle ma shown-in Fig. 7.

By referring to Fig. 11" it will be seen t at the ignition switch I 21 islocated' inthe conductor I53 and that between theco'nd'uctor I53 and the conductor I 45'is located the primary'l54 of the transformer I05 to which [the terminals I03" "of the spark gapigniter are iconnectedi The, closure of'the switch 'I3Ij by movement of 'the ai niature I30 to the pole I29 startsthe momma, 'tlie fan' 21 and theffeed plate 51, while at the "same time the plow 19fis moved toward the'cen'ter of the feed mat =51;, the a ve ;I II is opened and the electric ig it 1 I with the lockout switch I33 closed; the rnotor' When the gases flowing through the flue II3 become sufiiciently heated the shaft II6 will be rocked to move the inner carrier I I8 from the position shown in Fig. 4 to the position shown in Fig. 9, whereupon the hold-in switch I26 will be closed and the motor switch I3I, the pull-in switch I25, and the ignition switch I21 remain closed. Fig. 9 represents the positions of the switches I25, I26, I21, and I3I for the starting period. If the stack switch element II5 does not become sufficiently heated within a predetermined period of time to close the hold-in switch I26, say withina minute and a half, the heat generated by the resistor I35 will be suflicient to warp the flexible element I36 and enable the trip device I34 to open the switch I33, whereupon the main supply current through the conductor I43 will be opened thereby cutting oifzcurrent from feed plate 51.

the motor 44, the solenoid H and the ignition transformer I05. Thereupon the feeding of the fuel will be stopped and the flow of the gas through the nozzle I08 will be cut off. Before the furnace can be restarted the trip device I34 must be manually reset by actuation of the knob I31. Under normal conditions, however, the hold-in switch I26 will be closed thereby short-circuiting the resistor I35 and preventing further heating thereof. Continued heating of the stack element II will rock the shaft 1 I6 to a greater angle to move the carrier II1 to its position shown in Fig.

which represents the running positions of the switches I25, I26 and I21 or their positions when the feeder is running after the transient or starting period. When the switches I25 and I21 are moved from their positions shown in Fig. 9 to their positions shown in Fig. 10 they are both opened and consequently the ignition switch I21 will cut off the current from the electro-magnets 91 and I I0 and from the primary I54 of the ignition transformer I05. The plow 19 will then be moved by the spring 9| back to its adjusted position where it will operate to scoop the predetermined quantity of powdered coal from the annular passage-waytfl during each rotation of the The spark gap igniter I03 will-be discontinued but the motor 44 will continue to operate the fan 21 and the mixture of air and powdered coal will continue to be delivered for combustion, into the combustion chambers I5 and I6. So long as the thermostatic switch I40 remains in the position shown in Fig. 11 the secondary I28 will continue to act to hold the armature I30 against the pole I29 and therefore hold the motor switch I3I closed. When the room temperature reaches a predetermined point the thermostatic switch I40 will be tilted to the opposite position from that shown in Fig. 11 to effect closure of the contacts I55. Thereupon the circuit of the secondary winding I28 will be opened and consequently the armature I30 will be released and the switch I3I will be opened which will result in opening the motor circuit and stopping the rotation of the feed plate51 and the fan 21 automatically.

When the contacts I55 are closed a circuit is completed through the secondary winding I39. The voltage of this secondary winding is relatively low and insufficient to energize the electromagnet to move the armature I30. The winding I39 therefore acts merely as a. transformer secondary and the switch I3I remains open. As soon as the operation of the furnace is discontinued the stack element II5 tends to cool sufliciently to open the hold-in switch I26 and close the pull-in switch I25 and the ignition switch I21.

'ping of the lockout switch I33.

' operation of the thermostatic switch I40 does not stop the operation of the motor and the fan the holdein switch I26 will remain closed. Consequently upon the closure of the contacts I55 the auxiliary heating resistance I56 will effect trip- The resistance I56 may be such as to take a longer period of time than is taken by the resistance I35 to effect the opening of the switch I33. The circuit of this safety feature may be traced from the secondary I39 through the conductor I51, contacts I55, conductor I58,-hold-in switch I26, conductor I59, and resistance I56 to the other terminal ofthe secondary I39. If desired the voltage of the secondary I39 may be approximately 20 and that of the secondary I28 approximately 40 and the time for the resistance I35 to act may be 1 minutes and that for the resistance I56 to act may be 3 minutes.

Under normal conditions of operation the motor 44 will be stopped when the thermostatic switch I40 closes the contacts I55 and the stack element I I5 will act to move the parts back to the normal position shown in Fig. 4, whereupon the pull-in switch I25 will be closed, the ignition switch I21 will be closed, and the hold-in switch I26 will be opened. The resistances I56 and I35 will then be in series with each other through the switch I25 and the current through the resistances I35 and I 56 will then be insuflicient to effect opening of the look-out switch I33.

In the modification shown in Fig. 12 the same resistance I35 is employed as a safety device for both the starting period and the end of the de sired running period. The resistance I60 is an added resistance placed in circuit with the resistance I35 to prevent heating of the latter if the conditions are normal. During normal starting the thermostat closes the circuit from the will heat the resistance I35 sufficiently to effect opening of the lock-out switch I33. If, however, the hold-in switch I26 opens as it should the resistance I will be thrown in series with the resistance I 35 so as to prevent the latter from becoming suiliciently heated to open the switch I33.

In the modification shown in Fig. 13 the switch I26 is shown in position to deflect current from the heating resistance I35 through the resistance I6I. The circuit will then be from the secondary I28 through the conductor I50, switch I40, conductors I49, I53, switch I26, conductor I59, resistance I6I and conductor I41 to the other terminalof the secondary I28. So long as the pull-in switch I25 remains closed the resistance I6I will be in parallel with the resistance I35 and there will be sufficient current by-passed around the resistance I35 to prevent the latter from heating sufficiently to open the lock-out switch I33. When the pull-in switch I25 opens, the circuit from the secondary I26 will be through the resistance I6I alone and such resistance will cut down the current so that the switches I40 and I26 will not be overheated.

When the room thermostat tilts to 'close the contacts I55 a circuit will be closed from the low voltage secondary I39 through the conductor 2400 F. sothat irrespective of the temperature of I51, contacts I55, conductors I49, I58, switch I26, conductor I59 and resistance I62 to the other terminal of the low voltage secondary I39. The resistance I62 will cut down the current in the circuit secondary to prevent overheating of the contacts I55 and I26. In the same manner the resistance I56 in Fig. 11 may be used to cut down the current in the circuit of the secondary I39 and not be used as an auxiliary heater. However, if desired the resistance I62 in Fig. 13 may be used as an auxiliary heater to effect the opening of the look-out switch I33 if such abnormal conditions should occur as to unduly prolong the heating of the stack element H in the flue II3. Such abnormal condition will unduly prolong the closure of the switch I26 and consequently the heating resistance I62 connected to the low voltage seco'ndary I39 will eifect the opening of the look-out switch I33 after a pre-determined length of time. That is to say, both in the form shown in Fig. 11 and in the modification shown in Fig. 13 auxiliary heating resistances may be employed as safety features so as to operate after a longer interval than taken by the resistance I35 to automatically open the lock-out switch I33 when abnormal conditions of heating unduly prolong'the heating of the stack element H5.

It should also be noted that various hook-ups may be employed for the electrical circuit and connections shown in Figs. 11, 12, and 13 without altering the positions of the switches shown in Fig. 4. Various results may be obtained by rewiring and by use of the auxiliary heating resistances either to eifect the opening of the lockout switch I33 or by serving to protect the switches I26, I55.

While in some furnaces a pulverized fuel burner may be provided without having connected thereto the ignition or preliminary combustion chamber I5, such burner would require continued burning of gas at the gas burner nozzle I08 during the burning of the pulverized fuel so as to assure the continued burning of the latter. That is to say in a thermostatically controlled heating system, certain furnaces may at certain times become so cooled that when started in operation the cooling effect on the flame of. burning pulverized coal may be suflicient to cause the same to be extinguished if the gas flame from the nozzle I08 is not maintained. When the preliminary combustion chamber I5 is omitted I therefore prefer to so arrange the'electro-magnetic valve structure I ID as to be dependent on the switch I3I alone. This may be done by placing the electro-magnet of this valve structure in the motor circuit direct in the conductor I5I, I52 or I45 shown in Fig. 11. Then the gas will continue to burn at the nozzle I08 whenever the pulverized fuel burns at the nozzle 22 and the fuel flame will not be extinguished but will be maintained so long as the motor 44 operates the feeding mechanism and the blower.

However; it is highly desirable to reduce the consumption of the gas and I therefore prefer to include the preliminary combustion chamber I5 so that the gas may be cut off during the running period of the furnace. The refractory lining I8 of the preliminary combustion chamber becomes sumciently heated during the starting period to act continuously during the running period to maintain the pulverized fuel flame. For instance, such refractory lining may reach a temperature during the running period of approximately directly connected to the motor 44 the speed of rotation of the feed plate 51 is greatly reduced by reason of the speed reduction gearing 68, 61 and 63, 62. Since the intense heat of the fuel flame maintains the refractory lining I8 heated to a high temperature the pulverized coal may be burned with maximum efficiency and therefore the consumption of the fuel may be reduced to a minimum. For instance, I have found by actual test of a practical heating system such as that disclosed herein. that the feed of the pulverized coal to the fan need be no greater than one cubic foot in a period of twelve hours while burning of the pulverized coal in the furnace is being continuously sustained without theburning of any gas from the pipe I01 and burner nozzle I08 during the running period.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the .claim hereto appended, and I wish, therefore, not to be restricted to the precise construction herein disclosed.

Having thus describedand shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

In a furnace system, the combination with a furnace constructed and adapted for domestic operation and having a main combustion chamber, of an ignition chamber within said furnace and within said main combustion chamber, feeding means for supplying pulverized fuel mixed with air to said ignition chamber for initial com.- bush'on, said feeding means including a rotating plate, an adjustable non-rotating plow positioned to remove material from said plate, a fan, means directing material removed from said plate to said fan, and means fed by said fan and directing pulverized coal mixed with air to said ignition chamber as aforesaid; electro-magnetic means for adjusting said plow to increase the feeding rate of said feeding means during a flame starting period whereby the ignition chamber becomes sufficiently heated during the flame starting to act continuously during a following running period to maintain combustion of the mixture of pulverized fuel and air, ignition means for igniting said inixture, and automatic thermostatically controlled means constructed and arranged to effect operation of said ignition means, said feeding means and said plow to initiate combustion with the mixture of pulverized coal and air fed at EARLE V. FRANCIS. 

